1. Scope of the Invention
The present invention relates to centrifuge rotors, and in particular, to a centrifuge rotor having a segmented core supported by a composite ring.
2. Description of Related Art
Centrifuge rotors have been formed from isotropic metal billets. As the rotor is spun at high speed upon centrifugation, centrifugal forces are generated which result in internal stresses in the rotor. The critical internal stresses are tensile in nature and oriented in the radial and circumferential directions. The magnitude of the internal stresses depends on density, geometry and rotational speed of the rotor. The internal stresses increase with increasing rotation speed until a critical stress state is reached and the rotor structure fails. Functional rotors have holes drilled near their perimeters which necessarily weakens the solid isotropic rotor core.
For ultracentrifuges, hybrid metal and composite rotor systems have been proposed. In U.S. Pat. No. 5,057,071 which has been commonly assigned to the assignee of the present invention, a hybrid centrifuge rotor is disclosed which has an aluminum rotor core body shrink fitted in a ring made of composite material. The ring alters the stress state in the rotor core which results in higher permissible rotation speed before failure of the core. The ring which is made of a material reinforced in the circumferential direction can withstand high circumferential tensile stress. This allows the ring to support the radial centrifugal forces imparted by the core and prevent excessive deformation of the core which would otherwise lead to build-up of internal critical tensile stresses in the core. So far, this hybrid design has been applied to small sample capacity rotors.
However, full advantage of the structural capabilities of the support ring has not been taken by current designs. That is, in the event of rotor failure, the core body will likely fail before failure of the composite support ring.